This invention relates to aircraft cockpit projection displays, projection liquids crystal displays (LCD), and more specifically to illumination of LCD cockpit projections displays.
While cathode ray tube (CRT) and color active matrix liquid crystal display (AMLCD) technologies remain a viable display media for some cockpit applications, projection displays offer several unique advantages that render them highly attractive for aircraft applications.
Projection display technology provides an important advantage over other competing technologies. A single compact optical engine design may be utilized for a display image source for varied display sizes, achieving a scaleable display design. An optical engine comprises an image engine that generates the image and projection optics that project the image on a screen. A type of image engine that may be used is a reflective micro LCD device with a size of less than one inch diagonal that is manufactured on silicon. One projection optical engine combined with slightly modified folded optics may be used for displays ranging in size from 5xe2x80x3 square to 32xe2x80x3 diagonal. This flexibility allows leveraging a current design into new products, which results in lower development costs and faster timing to market. Projection display technology will also enable customers to benefit from continuing advances in commercial projection components without having to undergo major system changes to current products. For example, as the commercial market drives higher resolution and more efficient reflective LCDs and lamps, projection display products may incorporate these improvements by replacing individual components with minimal impact to the system. Projection displays offer performance such as luminance, contrast ratio, and chromaticity equal or superior to an AMLCD. The versatility of projection displays makes them a viable candidate technology for both military and commercial cockpit designs for new aircraft as well as cockpit redesigns for existing aircraft.
A projection LCD has several essential subsystems. Among them, the illumination subsystem is very critical. The failure of the illumination subsystem will immediately cause the projection display to stop displaying information. In order to use projection displays as aircraft cockpit displays, the illumination subsystem must be very reliable. When an aircraft is airborne under normal operating and environmental conditions, the illumination subsystem of a cockpit projection display should never fail. However, none of the current single lamp illumination systems has such a high reliability. What is needed is a projection display illumination configuration that provides illumination when a lamp fails.
A projection display with a high reliability illumination system is disclosed. Image signal sources provide image signals to be displayed on the projection display. Controllers convert the image signals from the image signal sources into signal formats for displaying and providing image drive signals. Image engines are connected to the controllers and form the display images for display. The illumination system provides light to illuminate the image engines to project the display images. The illumination system has variable power lamps to provide the light. Optical components conduct the light from the lamps to the image engines. The optical components are disposed to conduct the light to the image engines such that when a lamp fails illumination is maintained by varying the power to the remaining lamps. Projection optics channel the display image to a screen for displaying the image.
The illumination system further comprises a first channel with a first lamp providing light to a linear polarizer for polarizing the light from the first lamp into s-polarized light. A second lamp provides light to a first polarizing beam splitter for receiving the light from the second lamp and splitting the light from the second lamp into s-polarized light and p-polarized light. The first polarizing beam splitter receives the s-polarized light from the linear polarizer and combines the s-polarized light from the linear polarizer with the split p-polarized light. A second polarizing beam splitter receives the combined s- and p-polarized light from the first polarizing beam splitter and splits the combined s- and p-polarized light into s-polarized light and p-polarized light. A first mirror reflects the s-polarized light from the second polarizing beam splitter. A first half-wave retarder receives the s-polarized light reflected from the first mirror and shifts the s-polarized light to p-polarized light. A first converging lens combines the p-polarized light from the second polarizing beam splitter and the p-polarized light from the first half-wave retarder. A first light pipe channels the combined light from the converging lens to a first image engine.
The illumination system may further comprise a second channel with a third lamp for providing light. A third polarizing beam splitter receives the light from the third lamp and splits the light from the third lamp into s-polarized light and p-polarized light and receives the s-polarized light from the first polarizing beam splitter and combines the s-polarized light from the first polarizing beam splitter with the split p-polarized light. A fourth polarizing beam splitter receives the combined s- and p-polarized light from the third polarizing beam splitter and splits the combined s- and p-polarized light into s-polarized light and p-polarized light. A second mirror reflects the s-polarized light from the fourth polarizing beam splitter. A second half-wave retarder receives the s-polarized light reflected from the mirror and shifts it to p-polarized light. A second converging lens combines the p-polarized light from the fourth polarizing beam splitter and the p-polarized light from the second half-wave retarder. A second light pipe channels the combined light from the converging lens to a second image engine.
A lamp controller powers the lamps and a lamp sensor detects a failure of one of the lamps and causes the lamp controller to adjust power to the operating lamps to maintain illumination of the screen.
It is an object of the present invention to provide an illumination system that provides light for a projection display when a lamp fails.
It is an object of the present invention to provide a multi-channel LCD projection display with an illumination system with high reliability.
It is an advantage of the present invention to maintain illumination of a projection display automatically when a lamp fails.
It is an advantage of the present invention to easily expand to more channels as required.
It is a feature of the present invention to use commercially available components.